'The Sontaran Experiment' (2 Parts) Story Code '4B' by Bob Baker and Dave Martin

Arriving on a desolate and deserted Earth, the Doctor, Sarah and Harry meet a group of stranded astronauts from a human colony, GalSec, who have been lured to the planet by a fake distress call. One of the astronauts, Roth, tells Sarah of an alien who is conducting horrific experiments on him and his crewmates, but then he and Sarah are captured by the alien's robot, and taken to its master. Sarah recognises the alien as a Sontaran, a race of cloned warriors. The Sontaran, Field-Major Styre, is compiling a report on the physical and mental capabilities of humans, prior to an invasion of the galaxy. Styre subjects Sarah to his cruel tests, but the Doctor challenges him to unarmed combat, and the Sontaran agrees. While Styre is distracted, Harry enters his ship and uses the Doctors' sonic screwdriver to remove the vital terullian diode bypass transformer. Styre is quickly weakened in the unfamiliar gravity of Earth, and returns to his ship in order to re-energise himself, but he is drained of all of his energy instead, and dies. The Doctor contacts the Sontaran fleet using Styres' equipment, and warns their Marshall that without Styre's information they cannot invade the planet. The Doctor and his friends return to space station Nerva.

Tom Baker (Doctor Who), Elisabeth Sladen (Sarah Jane Smith), Ian Marter (Harry Sullivan), Donald Douglas (Vural), Glyn Jones (Krans), Peter Walshe (Erak), Kevin Lindsay (Styre / Styre and The Marshal), Peter Rutherford (Roth), Terry Walsh (Zake), Brian Ellis (Prisoner)

Produced by Barry Letts
Directed by Rodney Bennett

TX:
Part 1 - 22nd February, 1975 @ 5.30pm - 5.55pm
Part 2 - 1st March, 1975 @ 5.30pm - 5.55pm

Notes:
*Featuring the Fourth Doctor, Sarah and Harry

*Working title: 'The Destructors'